Heptametallic high‑entropy nanozyme‑based biosensors for detecting bacterial pathogens in food and infected wound

Rapid and sensitive on-site detection of bacteria in food and infected wounds is vital for public health. Herein, we report a heptametallic high‑entropy nanozyme (H-HEzyme) and develop an amplification-free and label-free colorimetric platform for catalase (CAT)-positive pathogen detection. The H-HEzyme possessed excellent peroxidase-like activity, thanks to its unique high-entropy structure that optimized active-site properties. The assay relies on competitive H₂O₂ catalysis between the H-HEzyme and bacterial CAT. Specificially, the H-HEzyme catalyzes H₂O₂ to generate hydroxyl radicals (·OH), which oxidize 3,3',5,5'- tetramethylbenzidine (TMB) into a blue product; whereas CAT rapidly decomposes H₂O₂, enabling a "signal-off" colorimetric signal linearly correlated with bacterial concentration for quantification. The developed biosensor successfully quantified Staphylococcus aureus (SA) in contaminated food samples (milk, juice), achieving satisfactory recoveries of 87.79-112.48% with good reproducibility. In addition, the platform detected methicillin-resistant S. aureus (MRSA) in infected wound models, achieving a detection limit of 10⁴ CFU/mL-below the clinical diagnostic threshold for wound infection (10⁵ CFU/mL). With rapid response, simple operation and minimal equipment requirement, this strategy extends the application of high-entropy materials in nanozyme biosensing, and offers a practical route for rapid, on-site pathogen detection in food safety and clinical settings.